CN110778475B

CN110778475B - Hydraulic rotary machine

Info

Publication number: CN110778475B
Application number: CN201910624601.2A
Authority: CN
Inventors: 森田启; 菅野直纪; 前川智史
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2018-07-12
Filing date: 2019-07-11
Publication date: 2021-12-21
Anticipated expiration: 2039-07-11
Also published as: EP3594497A1; EP3594497B1; JP7044652B2; US10920757B2; JP2020008006A; CN110778475A; US20200018298A1

Abstract

Provided is a hydraulic rotary machine which reduces the rotation delay of a retainer relative to a cylinder and restrains a piston arranged between the retainer and the cylinder from contacting with surrounding components. A piston pump (1) is provided with a rotating shaft (11), a cylinder block (12), a piston head (13), a piston rod (14), a retainer (15), a swash plate (16), and a tilt adjustment mechanism (17). If the tilting adjustment mechanism (17) swings the swash plate (16), the discharge amount of the piston pump (1) can be changed. A retainer (15) that rotates together with the piston head (13) and the piston rod (14) is supported by a retainer bushing (11A) provided on the rotating shaft (11). The retainer (15) and the retainer bush (11A) can rotate integrally around the central axis of the rotating shaft (11) and the retainer (15) swings around the Spherical Center (SC) by the engagement of the ball stud (11C) of the retainer bush (11A) and the spherical pin groove (15S) of the retainer (15).

Description

Hydraulic rotary machine

Technical Field

The present invention relates to a hydraulic rotary machine that can be used as a hydraulic pump and a hydraulic motor.

Background

Conventionally, a variable displacement hydraulic rotary machine which can be used as a hydraulic pump and a hydraulic motor is known. Such a hydraulic rotary machine includes a housing, a rotary shaft, a cylinder, and a plurality of pistons. The rotating shaft is rotatably supported by the housing. The cylinder block includes a plurality of cylinders formed around a central axis of the rotation shaft, and rotates together with the rotation shaft. The pistons are housed in a plurality of cylinders of the cylinder block, respectively, and reciprocate in accordance with the rotation of the cylinder block.

When the hydraulic rotary machine is used as a hydraulic pump, the cylinder rotates together with the rotary shaft by rotating the rotary shaft by an output of a predetermined drive unit, and the pistons reciprocate. At this time, the hydraulic oil flows into the cylinder of the cylinder from the predetermined low-pressure port, is pressurized by the piston, and is discharged from the predetermined high-pressure port.

On the other hand, when the hydraulic rotary machine is used as a hydraulic motor, high-pressure hydraulic oil is introduced into the cylinder of the cylinder from the high-pressure port, and the introduced hydraulic oil acts on the piston. After the reciprocating motion of the piston rotates the rotary shaft together with the cylinder, the working oil is discharged from the low-pressure port.

Patent document 1 discloses a swash plate type variable displacement hydraulic rotary machine. The hydraulic rotary machine includes, in addition to the above-described configuration, a holder bush, a holder, a swash plate, a thrust bearing, and a tilt adjustment mechanism. The retainer bush includes a spherical bush outer circumferential surface having a convex shape on the outer side in the radial direction of rotation of the rotary shaft, and is supported by the rotary shaft so as to be rotatable in conjunction with the rotation of the rotary shaft. The retainer includes a retainer inner circumferential surface having a concave spherical shape and slidable relative to the bushing outer circumferential surface. The retainer is supported by the retainer bushing so as to be swingable around an axis perpendicular to the rotation axis. Further, a swash plate is disposed opposite to the retainer on the opposite side to the cylinder axial direction, and is supported by the housing so as to be swingable around the axial center. The thrust bearing is interposed in the axial direction between the swash plate and the retainer, and supports the retainer so that the retainer can rotate around the central axis with respect to the swash plate. The tilt adjustment mechanism adjusts the amount of movement in the axial direction in the reciprocating motion of the piston by swinging the swash plate about the axis and swinging the retainer about the axis while bringing the inner peripheral surface of the retainer into sliding contact with the outer peripheral surface of the bushing.

According to such a hydraulic rotary machine, since the retainer and the swash plate are connected by the thrust bearing, it is possible to suppress the sliding resistance generated by the conventional swash plate type hydraulic pump. Further, since the reciprocating pistons are not in direct sliding contact with the swash plate, the amount of leakage of the working oil supplied as the lubricant can be set small. As a result, the volumetric efficiency of the hydraulic rotary machine can be improved.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-180448.

Disclosure of Invention

Problems to be solved by the invention

In the hydraulic rotary machine described in patent document 1, a cylinder rotates integrally with a rotary shaft. On the other hand, the retainer receives a rotational force from the cylinder via the piston, and rotates so as to follow the cylinder. In this case, a phase delay is liable to occur between the holder and the cylinder. As a result, the piston comes into contact with the cylinder or the retainer, and a part of each component may be damaged.

The present invention has been made in view of the above problems, and an object thereof is to provide a hydraulic rotary machine in which a rotation delay of a retainer with respect to a cylinder is reduced, and contact between a piston interposed therebetween and a surrounding member is suppressed.

Means for solving the problems

A hydraulic rotary machine according to an aspect of the present invention is a variable displacement hydraulic rotary machine including: a housing; a rotating shaft rotatably supported by the housing; a cylinder block including a plurality of cylinders disposed at intervals around the rotary shaft and rotating around a central axis of the rotary shaft integrally with the rotary shaft; a plurality of pistons which are respectively accommodated in the plurality of cylinders of the cylinder block and reciprocate in the cylinders along the axial direction of the rotation as the cylinder block rotates; a retainer bush including a bush outer circumferential surface having a spherical shape in which the outer side in the radial direction of rotation of the rotary shaft is convex, and supported by the rotary shaft so as to be rotatable around the central axis together with the rotary shaft; a retainer including a retainer inner circumferential surface having a concave spherical shape disposed to face the bushing outer circumferential surface, and supported by the retainer bushing so as to be swingable about an axis perpendicular to the rotation axis; a plurality of piston rods arranged to extend in the axial direction, each of the plurality of pistons being connected to the retainer, and rotating the retainer about the central axis in conjunction with rotation of the plurality of pistons about the central axis; a swash plate disposed opposite to the retainer on a side opposite to the cylinder block in the axial direction, and supported by the housing so as to be swingable around the axis; a thrust bearing interposed between the swash plate and the retainer in the axial direction, the thrust bearing supporting the retainer so that the retainer can rotate around the central axis with respect to the swash plate; and a tilt adjustment mechanism for adjusting the amount of axial movement of the piston in the reciprocating motion by swinging the swash plate about the axis, while relatively displacing the inner circumferential surface of the retainer and the outer circumferential surface of the bushing, and swinging the retainer about the axis via the thrust bearing; the retainer bushing has at least one protrusion protruding from the outer peripheral surface of the bushing outward in the radial direction, and the distal end of the protrusion has a spherical shape; at least one groove portion extending in a swinging direction of the retainer around the shaft center is formed in the inner peripheral surface of the retainer; the retainer and the retainer bushing are integrally rotatable around the central axis by the engagement of the at least one protrusion with the at least one groove, and the retainer is swingable around the axis by the movement of the at least one protrusion in the at least one groove.

According to this configuration, the hydraulic rotary machine can function as a hydraulic pump or a hydraulic motor by the cylinder body rotating together with the rotary shaft and the piston reciprocating in the cylinder. Since the retainer and the swash plate are connected by the power bearing, the sliding resistance during rotation of the retainer can be reduced. Further, since the reciprocating pistons are not in direct sliding contact with the swash plate, the amount of leakage of the working oil supplied as the lubricant can be set small. As a result, the volumetric efficiency of the hydraulic rotary machine can be improved. Further, the holder rotating together with the cylinder block is supported by a holder bush provided to the rotating shaft. The retainer bushing has at least one protrusion and the retainer has at least one groove. The retainer and the retainer bushing are integrally rotatable about the central axis by engaging the at least one protrusion with the at least one groove, and the retainer is swingable about the central axis by moving the at least one protrusion in the at least one groove. Therefore, the rotational phase of the rotary shaft and the rotational phase of the retainer substantially coincide with each other, and therefore, the rotational delay of the retainer with respect to the cylinder can be reduced. As a result, abnormal inclination of the piston rod is suppressed, and contact between the piston and the piston rod interposed between the cylinder and the retainer and surrounding members such as the retainer and the cylinder is suppressed. As a result, the durability of the hydraulic rotary machine can be improved.

In the above configuration, it is preferable that the at least one protrusion includes a plurality of protrusions arranged at intervals from each other along a rotation direction of the rotation shaft; the at least one groove includes a plurality of grooves arranged at intervals along the rotation direction.

According to this configuration, the rotational phase of the rotary shaft and the rotational phase of the cage can be stably substantially matched.

In the above-described configuration, it is preferable that the plurality of grooves have a concave circular shape when viewed in a cross section orthogonal to the central axis; the curvature of the circular shape of the plurality of groove portions is set to be the same as the curvature of the spherical shape of the tip end portions of the plurality of protrusions.

According to this configuration, the surface pressure generated at the distal end of the projection is made uniform, and the durability of the projection can be improved. Further, the sliding resistance between the protrusion and the groove when the retainer rotates is reduced, and the efficiency of the hydraulic rotary machine can be improved.

In the above-described configuration, it is preferable that the plurality of projections be constituted by an even number of the projections arranged at equal intervals around the central axis; the plurality of grooves are formed by the same number of grooves as the plurality of projections, which are arranged at equal intervals around the central axis.

According to this configuration, the retainer can be stably swung about the shaft center.

In the above-described configuration, it is preferable that the plurality of pistons be constituted by an odd number of the pistons arranged at equal intervals around the central axis; the plurality of piston rods are constituted by the same number of piston rods as the plurality of pistons arranged at equal intervals around the central axis.

According to this configuration, the pulsation of the hydraulic pressure generated when the cylinder is rotationally driven can be reduced.

Effects of the invention

According to the present invention, it is possible to provide a hydraulic rotary machine in which a rotation delay of a retainer with respect to a cylinder is reduced and contact between a piston interposed therebetween and a surrounding member is suppressed.

Drawings

Fig. 1 is a cross-sectional view of a hydraulic rotary machine according to an embodiment of the present invention, which is used as a hydraulic pump.

Fig. 2 is an enlarged cross-sectional view of a portion of the hydraulic rotary machine of fig. 1.

Fig. 3A is a cross-sectional view of the retainer of the hydraulic rotary machine of fig. 1, and is an enlarged side view showing a part of the retainer and the retainer bushing.

Fig. 3B is a side view showing a retainer and a retainer bushing of the hydraulic rotary machine of fig. 1.

Fig. 4A is a schematic bottom view showing a rotary shaft, a retainer, and a retainer bushing of the hydraulic rotary machine of fig. 1.

Fig. 4B is a schematic front view showing a rotary shaft, a retainer, and a retainer bushing of the hydraulic rotary machine of fig. 1.

Fig. 5 is a sectional view showing a state in which a swash plate is inclined in the hydraulic rotary machine of fig. 1.

Fig. 6A is a schematic diagram showing a rotation locus of a piston rod in a case where a swash plate is not tilted in a hydraulic rotary machine according to an embodiment of the present invention.

Fig. 6B is a schematic diagram showing a rotation locus of a piston rod in a case where a swash plate is inclined in a hydraulic rotary machine according to an embodiment of the present invention.

Fig. 7 is an enlarged sectional view for explaining the swing of a piston rod in the hydraulic rotary machine according to the embodiment of the present invention.

Fig. 8 is a cross-sectional view of a hydraulic rotary machine according to a modified embodiment of the present invention when used as a hydraulic motor.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view of a piston pump 1 according to an embodiment of a hydraulic rotary machine of the present invention. Fig. 2 is an enlarged cross-sectional view of a portion of the piston pump 1 of fig. 1. Fig. 3A is a cross-sectional view of the retainer 15 of the piston pump 1 in fig. 1, and is an enlarged side view showing a part of the retainer 15 and the retainer bushing 11A. Fig. 3B is a side view showing the retainer 15 and the retainer bush 11A of the piston pump 1 of fig. 1. Fig. 4A is a schematic bottom view showing the rotary shaft 11, the retainer 15, and the retainer bush 11A of the piston pump 1 of fig. 1. Fig. 4B is a schematic front view showing the rotary shaft 11, the retainer 15, and the retainer bush 11A of the piston pump 1 of fig. 1. Fig. 5 is a cross-sectional view showing a state in which a swash plate 16, which will be described later, is tilted in the piston pump 1 of fig. 1. Fig. 6A is a schematic diagram showing the rotational locus of the piston rod 14 in the case where the swash plate 16 is not tilted in the piston pump 1, and fig. 6B is a schematic diagram showing the rotational locus of the piston rod 14 in the case where the swash plate 16 is tilted. Fig. 7 is an enlarged cross-sectional view for explaining the oscillation of the piston rod 14 in the piston pump 1. In the drawings, the directions "up", "down", "front", and "rear" are shown hereinafter, but the directions are presented for convenience of explanation of the structure of the piston pump 1 according to the present embodiment, and the usage of the piston pump 1 is not limited. In fig. 1 and 5, the holder bush 11A, the plunger 12, the piston head 13, the piston rod 14, and the holder 15 are vertically substantially symmetrical about the rotation axis 11 for ease of explanation and understanding. In the present embodiment, as will be described later, nine (odd number) piston heads 13 and piston rods 14 are arranged around the rotation shaft 11. Therefore, the lower piston head 13 and the piston rod 14 shown in fig. 1 and 5 are actually arranged at positions offset in the rotation direction of the rotary shaft 11 from the positions shown in fig. 1 and 5 (the same applies to the spherical pin groove 15S and the ball stud 11C described later). The same applies to fig. 8 described later.

The variable displacement piston pump 1 according to the present embodiment is connected to a drive unit 100 such as an engine, and functions as a hydraulic pump that discharges working oil. The piston pump 1 includes a housing 10, a rotary shaft 11, a cylinder 12, a plurality of piston heads 13 (pistons), and a piston rod 14. Further, the piston pump 1 includes a holder 15, a swash plate 16, a tilt adjustment mechanism 17, a thrust bearing 18, and a swash plate receiving portion 19 (swash plate supporting portion).

The casing 10 functions as a case that supports the respective components of the piston pump 1. The rotary shaft 11 is rotatably supported by the housing 10. The rotary shaft 11 is coupled to the driving unit 100, and is rotated in the direction of the arrow in fig. 5 by the rotational driving force generated by the driving unit 100. The left end side of the rotating shaft 11 is rotatably supported by a roller bearing 20 disposed in the housing 10. On the other hand, the right end side of the rotary shaft 11 is also rotatably supported by a needle bearing 21 disposed in the housing 10. Further, an oil seal 23 and an O-ring 24 are disposed on the left side of the roller bearing 20 to prevent leakage of the working oil in the piston pump 1. Further, a 1 st flow path 10A and a 2 nd flow path 10B for discharging and sucking the working oil are formed on the right end side of the casing 10.

The holder bush 11A is provided substantially at the center of the rotation shaft 11 in the lateral direction. The retainer bushing 11A is a cylindrical member whose outer peripheral surface (retainer bushing spherical surface portion 11B) (fig. 2) is formed in a spherical shape. The holder bush 11A is supported by the rotary shaft 11 so as to be rotatable about the central axis of the rotary shaft 11 in conjunction with the rotation of the rotary shaft 11. In the present embodiment, the holder bush 11A is fitted to the outer peripheral portion of the rotary shaft 11 so as to be rotatable integrally with the rotary shaft 11.

Referring to fig. 2, the retainer bushing spherical portion 11B (bushing outer circumferential surface) has a spherical shape with a 1 st curvature centered on the spherical center SC, which is convex outward in the radial direction of rotation of the rotary shaft 11. The spherical center SC is arranged on the center line (rotation axis) of the rotation shaft 11. The retainer bushing spherical portion 11B has a function of swingably supporting a retainer 15 described later. The holder bush 11A has a plurality of ball studs 11C (projections) (fig. 1, 3A, and 3B). The plurality of ball studs 11C are arranged at intervals along the rotation direction of the rotary shaft 11, and project outward in the radial direction from the retainer bushing spherical portion 11B. The tip portions of the plurality of ball pins 11C each have a spherical shape. In the present embodiment, a pin hole, not shown, is opened from the retainer bushing spherical portion 11B toward the inside of the retainer bushing 11A. By inserting the ball stud 11C into the pin hole, as shown in fig. 1, 3A, and 3B, the tip end portion of the ball stud 11C is disposed radially outward of the retainer bushing spherical portion 11B.

In the present embodiment, the plurality of ball pins 11C is formed of an even number of ball pins 11C, specifically, six ball pins 11C, which are arranged at equal intervals around the center axis of the rotation shaft 11 (fig. 3B).

The cylinder 12 is a substantially cylindrical unit disposed around the rotation shaft 11. The cylinder 12 is engaged with the rotary shaft 11 via a spline 11S. As a result, the cylinder 12 rotates around the central axis of the rotary shaft 11 integrally with the rotary shaft 11. Further, a bush 22 is inserted between the rotary shaft 11 and the inner circumferential surface of the cylinder 12 on the left side of the spline 11S. The bush 22 has a function of absorbing the swing of the cylinder 12 generated by the wobbling of the spline 11S when the cylinder 12 rotates.

Further, the cylinder block 12 includes a plurality of cylinders 12S arranged at intervals around the rotation shaft 11. The cylinder 12S is a cylindrical space extending in the left-right direction. In the present embodiment, nine cylinders 12S are provided around the rotary shaft 11 at equal intervals. A control opening 12T (see fig. 7) is formed in each cylinder 12S. On the other hand, a valve plate 25 is fixed between the cylinder block 12 and the right end portion of the housing 10. The valve plate 25 slides on the cylinder block 12 without rotating (see the sliding surface T in fig. 7). Valve plate 25 is a substantially disk-shaped member disposed around rotary shaft 11. The valve plate 25 has a plurality of valve openings 25H. Some of the valve openings 25H communicate with the 1 st channel 10A, and the other valve openings 25H communicate with the 2 nd channel 10B. If the cylinder block 12 rotates together with the rotary shaft 11, the control openings 12T (fig. 7) of the plurality of cylinders 12S sequentially communicate with the 1 st flow path 10A or the 2 nd flow path 10B via the valve opening portion 25H. In addition, when the hydraulic rotary machine functions as the piston pump 1 as in the present embodiment, the low-pressure side cylinder 12S communicates with the suction-side 1 st passage 10A, and the high-pressure side cylinder 12S communicates with the discharge-side 2 nd passage 10B (fig. 5). On the other hand, as in the modified embodiment described later, when the hydraulic rotary machine functions as the piston motor 1A (see fig. 8), the high-pressure side cylinder 12S communicates with the suction-side 2 nd flow path 10B, and the low-pressure side cylinder 12S communicates with the discharge-side 1 st flow path 10A.

The piston heads 13 are housed in the plurality of cylinders 12S of the cylinder body 12, respectively. The piston head 13 rotates around the center axis of the rotary shaft 11 together with the cylinder 12 while reciprocating in the cylinder 12S in the axial direction (left-right direction) in accordance with the rotation of the cylinder 12. As the piston head 13 reciprocates, the volume of the cylinder 12S varies, and the working oil is sucked and discharged.

The plurality of piston rods 14 are disposed so as to extend in the axial direction (left-right direction) of the rotary shaft 11, and connect the plurality of piston heads 13 and the holder 15, respectively. As a result, the piston rod 14 has a function of rotating the retainer 15 about the central axis in conjunction with the rotation of the plurality of piston heads 13 about the central axis. The piston rod 14 is a rod-shaped member having a substantially cylindrical shape. More specifically, the piston rod 14 includes a head-side end 141 (one end side) and a holder-side end 142 (the other end side). Further, an oil groove 143 extending in the left-right direction is formed inside piston head 13 and piston rod 14. The oil groove 143 feeds a part of the working oil in the cylinder 12S between the retainer-side end 142 and the retainer 15. As a result, when the rotary shaft 11 is rotated in accordance with the operation of the piston pump 1, the piston head 13, the piston rod 14, and the retainer 15 are prevented from being sintered.

The head-side end portion 141 is formed in a spherical shape, and is coupled to a hemispherical (spherical) piston head support portion 13S (fig. 7) (the 1 st coupling portion) formed inside the piston head 13. The head-side end 141 and the piston head support portion 13S are in surface contact with each other along the spherical surfaces thereof. That is, the head-side end 141 of the piston rod 14 and the piston head support portion 13S are coupled to be relatively rotatable. The left end of the head-side end 141 is locked by the head fixing ring 13A (fig. 1 and 7). Further, the head fixing ring 13A is fixed by a retaining ring 13B. With such a configuration, the head-side end portion 141 is supported by the piston head 13 so as to be swingable in the radial direction and the circumferential direction (around the central axis of the rotary shaft 11) of the rotation of the rotary shaft 11. Further, by coupling the head-side end portion 141 to the piston head 13, the plurality of piston heads 13 and the piston rods 14 rotate integrally with the rotary shaft 11.

Similarly, the retainer-side end 142 is formed in a spherical shape, and is fitted into and coupled to a hemispherical (spherical) retainer support portion 15D (fig. 7) formed inside the retainer 15 (the 2 nd coupling portion). Further, with such a configuration, the holder-side end portion 142 is supported by the holder 15 so as to be swingable in the radial direction and the circumferential direction (around the central axis of the rotation shaft) of the rotation shaft 11. The retainer-side end 142 and the retainer support portion 15D are in surface contact with each other along the spherical surface. That is, the holder-side end 142 of the piston rod 14 and the holder support portion 15D are coupled to each other so as to be relatively rotatable. Further, by coupling the holder-side end 142 and the holder 15, the plurality of piston rods 14 and the holder 15 rotate integrally with the rotary shaft 11.

The retainer 15 is disposed opposite to the cylinder 12 in the axial direction of the rotary shaft 11. The retainer 15 is an annular member having an inner peripheral surface (retainer spherical surface portion 15A) with a predetermined spherical shape. The retainer spherical surface portion 15A of the retainer 15 is disposed to face the retainer bushing spherical surface portion 11B of the retainer bushing 11A, and is slidably fitted to the retainer bushing spherical surface portion 11B. The retainer 15 is supported by the retainer bush 11A so as to be swingable around an axial center extending in a direction orthogonal to the rotation shaft 11 (a direction intersecting the rotation shaft 11 and orthogonal to the paper surface of fig. 1, a front-rear direction). The axis center extends in a direction perpendicular to the paper surface of fig. 2 through the spherical center SC of fig. 2.

Referring to fig. 2, the retainer 15 includes the retainer spherical surface portion 15A (retainer inner circumferential surface), the sliding portion 15B, the swash plate facing portion 15C (retainer outer circumferential surface), and the retainer support portion 15D (2 nd axial support portion).

The retainer spherical portion 15A is an inner peripheral surface of the retainer 15 continuously extending along the periphery of the center axis of the rotary shaft 11. The retainer spherical surface portion 15A has a spherical surface shape which is concave toward the radial outer side of the rotation of the rotary shaft 11 and has the same 1 st curvature as the retainer bushing spherical surface portion 11B. The holder 15 swings left and right about the spherical center SC of fig. 2 as a fulcrum in accordance with the swing of the swash plate 16. In the retainer spherical portion 15A of the retainer 15, a plurality of spherical pin grooves 15S (groove portions) are formed, the plurality of spherical pin grooves 15S being arranged at intervals along the rotational direction of the retainer 15 about the rotation shaft 11 and extending along the swing direction of the retainer 15 about the shaft center (fig. 1, 3A, 3B). The plurality of spherical pin grooves 15S have a concave circular shape when viewed in a cross section orthogonal to the central axis of the rotary shaft 11 (fig. 3B). In the present embodiment, the curvature of the circular shape of the plurality of spherical pin grooves 15S is set to be the same as the curvature of the spherical shape of the distal end portions of the plurality of ball pins 11C. As shown in fig. 2, when viewed along the spherical center SC, the spherical pin grooves 15S extend along the outer peripheral surface of the retainer bushing spherical surface portion 11B on the inner peripheral surface of the retainer 15 (retainer spherical surface portion 15A). Fig. 4A is a view of the holder 15 in a state of being swung and tilted as viewed from below, and fig. 4B is a view of the same state as viewed from the front.

The plurality of spherical pin grooves 15S are formed of the same number of spherical pin grooves 15S as the plurality of ball pins 11C, which are arranged at equal intervals around the central axis of the rotation shaft 11 (fig. 3B). Specifically, the plurality of spherical pin grooves 15S is formed by an even number of spherical pin grooves 15S, and more specifically, is formed by six spherical pin grooves 15S (fig. 3B). Further, a predetermined gap is formed between the retainer spherical portion 15A and the retainer bushing spherical portion 11B (fig. 3B).

In the present embodiment, the retainer 15 and the retainer bushing 11A are integrally rotatable about the central axis of the rotation shaft 11 by the engagement of the plurality of ball pins 11C with the plurality of spherical pin grooves 15S, respectively, and the retainer 15 is swingable about the spherical center SC by the relative movement of the plurality of ball pins 11C within the plurality of spherical pin grooves 15S. In fig. 3B, for the sake of explanation, a gap is provided between the tip end portion of the ball stud 11C and the spherical pin groove 15S, but since the curvatures of both are set to be the same as described above, the tip end portion of the ball stud 11C actually fits into the spherical pin groove 15S and comes into surface contact with each other.

The sliding portion 15B is formed by a left side surface of the holder 15, and is disposed to face the thrust bearing 18. When the holder 15 rotates together with the rotary shaft 11, the sliding portion 15B slides with respect to the thrust bearing 18. The swash plate facing portion 15C corresponds to the outer peripheral surface of the retainer 15 disposed radially outward of the retainer spherical portion 15A.

The swash plate 16 is supported swingably in the housing 10. In particular, the swash plate 16 is disposed opposite to the retainer 15 in the axial direction of the cylinder block 12. The swash plate 16 is swung by the tilt adjustment mechanism 17. The swash plate 16 is formed in a substantially hemispherical shape disposed around the rotary shaft 11 so as to face the holder 15, and includes a swash plate adjustment portion 161 extending from an upper end portion thereof. The swash plate adjusting portion 161 is moved left and right by the tilt adjusting mechanism 17. As a result, the swash plate 16 swings left and right about the spherical center SC of fig. 2 as a fulcrum. The swash plate 16 includes a bearing fixing portion 162 (fixing surface), a swash plate spherical surface portion 163 (supported portion), and a holder facing portion 164 (facing surface) in addition to the swash plate adjusting portion 161 described above.

The thrust bearing 18 is fixed to the bearing fixing portion 162. The bearing fixing portion 162 is an annular wall surface extending in a direction orthogonal to the axial direction of the rotary shaft 11. The swash plate spherical surface portion 163 is disposed leftward of the bearing fixing portion 162, in other words, is disposed on the opposite side of the bearing fixing portion 162 in the axial direction. The swash plate spherical surface portion 163 is constituted by a part of a spherical surface centered on a spherical center SC concentric with the retainer bushing spherical surface portion 11B. The spherical shape of the swash plate spherical portion 163 is constituted by the 2 nd curvature smaller than the 1 st curvature of the retainer bushing spherical portion 11B. In other words, referring to fig. 2, the spherical shape of the retainer bushing spherical portion 11B is formed by a shape along the 1 st virtual spherical surface SP1, and the spherical shape of the swash plate spherical portion 163 is formed by a shape along the 2 nd virtual spherical surface SP2 concentric with the 1 st virtual spherical surface SP 1. The radius of the 2 nd imaginary spherical surface SP2 (the radius of curvature of the swash plate spherical surface portion 163) is larger than the radius of the 1 st imaginary spherical surface SP1 (the radius of curvature of the retainer bushing spherical surface portion 11B).

The holder facing portion 164 is an inner peripheral surface of the swash plate 16 disposed to face the swash plate facing portion 15C of the holder 15 in the radial direction. Although not shown in detail in fig. 2, a predetermined gap is formed between the swash plate facing portion 15C and the retainer facing portion 164. In the present embodiment, the swash plate 16 is not in direct contact with the holder 15.

The tilt adjustment mechanism 17 is disposed above the cylinder 12. The tilt adjustment mechanism 17 swings the swash plate 16 to the left and right about the spherical center SC of fig. 2, thereby swinging the retainer 15 about the spherical center SC via the thrust bearing 18 while bringing the retainer spherical surface portion 15A into sliding contact with (relatively displacing) the retainer bushing spherical surface portion 11B. As a result, the tilt adjustment mechanism 17 adjusts the amount of axial movement in the reciprocating motion of the piston head 13. That is, the tilt adjustment mechanism 17 has a function of adjusting the flow rate discharge amount of the piston pump 1.

The tilt adjustment mechanism 17 includes a swash plate support portion 171, a 1 st tilt adjustment portion 172, and a 2 nd tilt adjustment portion 173. The swash plate support portion 171 is fitted into a recess formed in the upper end portion of the swash plate adjustment portion 161. The swash plate adjusting portion 161 is swung left and right by the driving force transmitted to the swash plate supporting portion 171. The 1 st tilt adjustment portion 172 biases the swash plate adjustment portion 161 from the right. Similarly, the 2 nd tilt adjustment portion 173 biases the swash plate adjustment portion 161 from the left. Since the 1 st tilt adjustment portion 172 and the 2 nd tilt adjustment portion 173 are configured in the same manner, the structure of the 1 st tilt adjustment portion 172 will be described below as an example.

The 1 st tilt adjustment portion 172 includes a tilt piston 174, an adjustment housing 175, a shaft 176, a tilt piston spring 178, and a fixing portion 179. The adjustment housing 175 supports the respective members of the 1 st tilt adjustment portion 172. The tilt piston 174 is slidable in the left-right direction inside the adjustment housing 175. The tip end portion (left end portion) of the tilt piston 174 abuts on the swash plate adjusting portion 161 of the swash plate 16. The shaft 176 is a shaft portion extending into the interior of the adjustment housing 175. The right end of the adjustment case 175 is fixed to the shaft 176 by a nut-shaped fixing portion 179. A tilt piston spring 178 formed of a coil spring is disposed between the inner peripheral portion of the tilt piston 174 and the adjustment housing 175. The tilt piston 174 biases the swash plate adjustment portion 161 leftward by the biasing force of the tilt piston spring 178. O-

rings

175A and 177A for preventing oil leakage are disposed in the adjustment case 175 and on the outer peripheral portion of the tilt stopper 177, respectively. The structure of the tilt adjustment mechanism 17 is not limited to the above, and may be any structure as long as the swash plate 16 is swung left and right about the spherical center SC in fig. 2.

The thrust bearing 18 is interposed between the swash plate 16 and the retainer 15 in the axial direction of the rotary shaft 11. Specifically, the thrust bearing 18 is disposed between the bearing fixing portion 162 of the swash plate 16 and the sliding portion 15B of the holder 15. The thrust bearing 18 supports the retainer 15 so that the retainer 15 can rotate about the center axis of the rotary shaft 11 with respect to the swash plate 16.

The swash plate receiving portion 19 (fig. 1) is disposed in the housing 10 so as to face the swash plate 16, and is a member having a substantially hemispherical shape. The swash plate receiving portion 19 includes a spherical surface 19A facing the swash plate spherical surface portion 163 (fig. 2) of the swash plate 16. The spherical surface 19A is formed with the same 2 nd curvature as the swash plate spherical surface portion 163 of the swash plate 16 (fig. 2). The swash plate receiving portion 19 supports the swash plate spherical portion 163 of the swash plate 16 so that the swash plate 16 can swing left and right about the spherical center SC. Therefore, if the swash plate 16 is swung left and right by the tilt adjustment mechanism 17, the swash plate spherical surface portion 163 is in surface contact with the spherical surface 19A while being in sliding contact therewith. As shown in fig. 2, the swash plate receiving portion 19 is disposed in the housing 10 so that the swash plate receiving portion 19 and the thrust bearing 18 sandwich a part of the swash plate 16 in the axial direction (left-right direction).

Further, the piston pump 1 includes a cylinder support portion 26 and a cylinder biasing spring 27 (fig. 1). The cylinder support 26 and the cylinder biasing spring 27 are disposed on the radial position side of the piston rod 14. The cylinder support 26 is an annular member that abuts against the retainer liner spherical surface portion 11B (fig. 2) of the retainer liner 11A. Further, the portion of the cylinder support portion 26 that contacts the retainer liner spherical surface portion 11B has a spherical surface shape having the same curvature as the retainer spherical surface portion 15A of the retainer 15. The cylinder biasing spring 27 is a spring member interposed between the cylinder support portion 26 and the cylinder 12. The cylinder biasing spring 27 biases the cylinder 12 toward the valve plate 25. When the cylinder 12 rotates, the elastic force of the cylinder biasing spring 27 reduces the swing in the axial direction (the left-right direction) of the cylinder 12.

When the tilt of the piston pump 1 is adjusted, the swash plate adjusting portion 161 is moved in the direction of arrow D1 (fig. 5) by the tilt adjustment mechanism 17 from the state shown in fig. 1. At this time, the position of the swash plate 16 after adjustment is determined by the balance between the external force applied to the swash plate support portion 171 (fig. 1) and the biasing force of the tilt piston spring 178 of the 1 st tilt adjustment portion 172 and the 2 nd tilt adjustment portion 173. As the swash plate adjusting portion 161 moves, the swash plate 16 smoothly swings in the direction of arrow D2 around the spherical center SC (fig. 2) along the spherical shape of the swash plate receiving portion 19. At this time, the retainer 15 swings in the arrow D3 and D4 directions along the retainer bush 11A and in the arrow direction of fig. 4B via the thrust bearing 18. At this time, the plurality of ball pins 11C are engaged with the plurality of spherical pin grooves 15S, respectively, and the plurality of ball pins 11C move in the plurality of spherical pin grooves 15S, whereby the retainer 15 can swing around the spherical center SC (axial center). Further, the piston head 13 coupled to the holder 15 via the piston rod 14 moves in the axial direction within the cylinder 12S in accordance with the swing of the holder 15. Specifically, in fig. 5, the uppermost piston head 13 moves leftward, and the lowermost piston head 13 moves rightward (fig. 5). As a result, the volume of each cylinder 12S changes with the rotation of the cylinder block 12. That is, the discharge capacity of the piston pump 1 is variable in accordance with the tilting of the swash plate 16.

In the present embodiment, as described above, nine cylinders 12S and piston heads 13 are arranged in the cylinder block 12. In this way, by setting the number of piston heads 13 and cylinders 12S arranged at equal intervals around the central axis of the rotary shaft 11 to an odd number and also setting the number of the plurality of piston rods 14 to the same number (odd number) as the number of piston heads 13, pulsation of the hydraulic pressure generated at the time of the rotational driving of the cylinder 12 is reduced. In other words, when the number of the cylinders 12S and the piston heads 13 is an even number, the pulsation of the hydraulic pressure of the cylinders 12S arranged symmetrically in the radial direction is increased by resonating with each other.

With reference to fig. 1 and 6A, a case will be described in which the swash plate 16 is not controlled to tilt, and the holder 15 is disposed so as to be orthogonal to the axial direction of the rotary shaft 11. In this case, the piston head 13 does not move in the axial direction in any phase during one rotation of the piston rod 14 about the center axis of the rotary shaft 11. Therefore, the rotational orbit of the holder-side end 142 of the piston rod 14 becomes a perfect circle P1. In this case, since the whirling motions of the nine piston heads 13 are cancelled out, the oscillation of the cylinder block 12 about the rotation axis does not occur.

On the other hand, with reference to fig. 5 and 6B, a case where the swash plate 16 is tilt-controlled and the displacement capacity of the piston pump 1 is larger than 0 will be described. In this case, the axial position of the piston head 13 changes according to the phase while the piston rod 14 rotates once around the center axis of the rotation shaft. As a result, as shown in fig. 6B, the rotational orbit of the holder-side end 142 of the piston rod 14 becomes an ellipse P2. In particular, the distance between the piston rod 14 and the rotation center of the rotation shaft 11 at the phase 0 degree and the phase 180 degree is shorter than that in the case of fig. 6A. On the other hand, in the phase 90 degrees and the phase 270 degrees, the distance between the piston rod 14 and the rotation center of the rotation shaft 11 becomes longer than that in the case of fig. 6A. In fig. 7, the piston rod 14 of fig. 6B with the phase of 0 degrees is shown in an enlarged manner. When the swash plate 16 is tilted as shown in fig. 5, the axis of the piston rod 14 moves from the 1 st virtual axis C1 to the 2 nd virtual axis C2 in the case of fig. 6A. At this time, the head-side end 141 of the piston rod 14 swings inside the piston head support portion 13S of the piston head 13. As described above, the rotational orbit of the piston rod 14 becomes the ellipse P2 by the posture change of the piston rod 14 in each phase. In this case, the whirling motion of the nine piston heads 13 is not cancelled out. As a result, the swing of the cylinder block 12 about the rotation axis is likely to be large.

In this case, the retainer 15 is supported by the retainer bushing 11A fitted to the rotary shaft 11 in the present embodiment. The retainer bush 15 has a plurality of ball studs 11C, and the retainer 15 has a plurality of spherical stud grooves 15S. Further, the retainer 15 and the retainer bushing 11A are integrally rotatable around the central axis of the rotation shaft 11 by the engagement of the plurality of ball pins 11C with the plurality of spherical pin grooves 15S, respectively, and the retainer 15 is swingable around the spherical center SC (axial center) by the relative movement of the plurality of ball pins 11C in the plurality of spherical pin grooves 15S. Therefore, if the rotary shaft 11 rotates, the rotary shaft 11, the holder 15, and the holder bush 11A rotate integrally around the central axis of the rotary shaft 11, while the plunger 12 rotates integrally with the rotary shaft 11. Therefore, since the rotational phase of the rotary shaft 11 and the rotational phase of the cage 15 substantially match each other, the rotational delay of the cage 15 with respect to the plunger 12 can be reduced. As a result, abnormal inclination of the piston rod 14 is suppressed, and contact between the piston head 13 and the piston rod 14 interposed between the plunger 12 and the retainer 15 and surrounding components such as the retainer 15 and the plunger 12 is suppressed. As a result, the durability of the piston pump 1 can be improved. Further, in the present embodiment, since the rotation shaft 11 can stably hold the rotation of the plurality of piston heads 13, the whirling motion of the piston heads 13 is suppressed. Further, since a predetermined gap is formed between the swash plate facing portion 15C of the retainer 15 and the retainer facing portion 164 of the swash plate 16, no forcible force is applied to the retainer 15 from the radial outside. Therefore, the degree of freedom of the retainer 15 is ensured, and the whirling motion of the piston head 13 is easily absorbed.

In the present embodiment, since the retainer spherical surface portion 15A of the retainer 15 and the retainer bushing spherical surface portion 11B of the retainer bushing 11A are formed of spherical surfaces having the same 1 st curvature, the retainer 15 can be easily rotated along the retainer bushing 11A during tilt adjustment. Further, since the swash plate receiving portion 19 has a spherical shape concentric with the spherical shape of the retainer bushing spherical portion 11B when viewed in cross section in fig. 1, the retainer 15 can be swiftly swung in conjunction with the swing of the swash plate 16. Therefore, tilting of the swash plate 16 is smoothly linked with movement of the holder 15, the piston rod 14, and the piston head 13, and responsiveness of tilting control can be improved. In addition, in such a configuration, since it is not necessary to tilt the cylinder 12 with respect to the rotary shaft 11 in order to adjust the discharge capacity of the piston pump 1, the tilting control mechanism of the piston pump 1 is suppressed from being complicated.

In the present embodiment, as shown in fig. 7, the head-side end 141 of the piston rod 14 is allowed to swing in the radial direction with respect to the piston head 13 (arrow DM in fig. 7), and the holder-side end 142 is allowed to swing in the radial direction with respect to the holder 15 (arrow DN in fig. 7). In other words, the head-side end 141 and the holder-side end 142 of the piston rod 14 have rotational degrees of freedom with respect to the piston head 13 and the holder 15, respectively. Therefore, the radial swing and sloshing of the piston head 13 occurring at the time of rotation of the cylinder 12 is absorbed by the swing of the piston rod 14. Further, along the spherical shapes of the head-side end 141 and the retainer-side end 142, a contact portion between the piston head 13 and the piston rod 14 and a contact portion between the piston rod 14 and the retainer 15 are formed. Therefore, the contact area between the piston rod and the piston rod 14 is increased, and the surface pressure of the piston rod 14 is reduced, thereby suppressing seizure of the piston rod 14 during driving. Further, since sintering is difficult even if the supply amount of the lubricating oil via the oil groove 143 (fig. 1) is small, the pump (volumetric) efficiency of the piston pump 1 can be improved.

Further, in the present embodiment, the retainer 15 and the swash plate 16 are connected by the thrust bearing 18. Therefore, the sliding resistance generated during rotation can be reduced as compared with other hydraulic rotary machines in which the members contact each other without passing through the bearing. Further, in the present embodiment, the reciprocating piston head 13 is not in direct contact with the swash plate 16. Therefore, the leakage amount of the working oil supplied as the lubricant to the sliding portion in the piston pump 1 can be set to be small, and the volumetric efficiency of the piston pump 1 (hydraulic rotary machine) can be improved. In the present embodiment, the retainer 15 is supported by the retainer bushing 11A, and a predetermined gap is formed between the swash plate facing portion 15C of the retainer 15 and the retainer facing portion 164 of the swash plate 16. Therefore, the dimension of the piston pump 1 in the radial direction can be set compact as compared with the case where a radial bearing is disposed between the retainer 15 and the swash plate 16.

Further, in the present embodiment, as shown in fig. 2, the swash plate receiving portion 19 is disposed in the housing 10 so that the swash plate receiving portion 19 and the thrust bearing 18 sandwich a part of the swash plate 16 in the axial direction. Therefore, even when a strong pressing force is applied to the retainer 15 in the left direction by the reciprocating motion of the piston head 13, the retainer 15 can be stably supported by the thrust bearing 18 and the swash plate 16.

Further, in the present embodiment, the plurality of spherical pin grooves 15S of the retainer 15 have a concave circular shape when viewed in a cross section orthogonal to the central axis of the rotary shaft 11 (fig. 3B). The curvature of the circular shape of the plurality of spherical pin grooves 15S is set to be the same as the curvature of the spherical shape of the distal end portions of the plurality of ball pins 11C of the retainer bushing 11A. With this configuration, the surface pressure generated at the tip end portion of the ball stud 11C is made uniform, and the durability of the ball stud 11C can be improved. Further, the sliding resistance between the ball stud 11C and the spherical pin groove 15S during rotation of the retainer 15 is reduced, and the efficiency of the piston pump 1 can be improved.

In the present embodiment, the plurality of ball pins 11C are formed by an even number of ball pins 11C arranged at equal intervals around the central axis of the rotation shaft 11, and the plurality of spherical pin grooves 15S are formed by the same number of spherical pin grooves 15S as the plurality of ball pins 11C arranged at equal intervals around the central axis. In this case, the holder 15 is stably supported by the holder bush 11A, and the holder 15 can be stably swung about the spherical center SC and rotated about the rotation shaft 11. The arrangement and number of the ball pins 11C and the ball pin grooves 15S are not limited to those described above, and for example, the number of the ball pins 11C and the number of the ball pin grooves 15S may be odd. In addition, when the piston pump 1 is used at a low load, at least one ball stud 11C and one spherical pin groove 15S may be provided. Further, by providing the plurality of ball pins 11C and the plurality of spherical pin grooves 15S, the rotational phase of the rotary shaft 11 and the rotational phase of the retainer 15 can be stably and substantially matched.

Further, in the present embodiment, the plurality of piston heads 13 are constituted by an odd number of piston heads 13 arranged at equal intervals around the central axis of the rotary shaft 11, and the plurality of piston rods 14 are constituted by the same number of piston rods 14 as the number of piston heads 13 arranged at equal intervals around the central axis. With such a configuration, the pulsation of the hydraulic pressure generated when the plunger 12 is rotationally driven can be reduced. However, the arrangement and number of piston heads 13 and piston rods 14 are not limited to the above. The number of piston heads 13 and piston rods 14 may be even when the pulsation of the hydraulic pressure is not excessively large, or when the pulsation of the hydraulic pressure can be solved by a structure other than the above-described arrangement and number of piston heads 13 and piston rods 14.

The piston pump 1 (hydraulic rotary machine) according to the embodiment of the present invention is explained above. The present invention is not limited to these embodiments. The hydraulic rotary machine according to the present invention may be a modified embodiment as described below.

(1) In the above-described embodiment, the piston pump 1 was described as a variable displacement hydraulic rotary machine, but the present invention is not limited to this. Fig. 8 is a cross-sectional view of a case where a hydraulic rotary machine according to a modified embodiment of the present invention is used as a piston motor 1A (hydraulic motor). For example, in the piston motor 1A of fig. 8, the swash plate 16 is swung in the direction of arrow D5 by the tilt adjustment mechanism 17. As a result, a phase opposite to that in the case of fig. 5 occurs at each piston head 13. In the plurality of cylinders 12S, the high-pressure working oil flows into the cylinder 12S having a small volume as indicated by an arrow DA. As a result, the inflowing hydraulic fluid acts on piston head 13, and pushes piston head 13 to the left. The moving force of the piston head 13 is converted into rotation of the cylinder 12 and the rotary shaft 11 via the holder 15. The piston motor 1A functions as a motor by rotating the rotary shaft 11 in the direction of the arrow in fig. 8. Further, if the piston head 13 on the high pressure side (the upper piston head 13 in fig. 8) moves to the low pressure side while rotating together with the holder 15, the working oil is discharged in the arrow DB direction. In the piston motor 1A of fig. 8, the retainer 15 is also swung along the spherical shape of the retainer bush 11A, thereby realizing variable displacement control of the piston motor 1A. Further, the head-side end portion and the holder-side end portion of the piston rod 14 are made to be at least radially swingable relative to the piston head 13 and the holder 15, whereby the whirling motion of the piston head 13 during the rotational driving is suppressed. Other operational effects can also be exhibited in the same manner as in the previous embodiment.

(2) In the above embodiment, the head-side end 141 and the holder-side end 142 of the piston rod 14 have spherical shapes, but the present invention is not limited to this. As shown in fig. 1, the head-side end 141 and the holder-side end 142 may have an arc shape when viewed in cross section along the axial direction of the rotary shaft 11, and may have a predetermined thickness in a direction perpendicular to the paper surface of fig. 1. In this case, the piston head support portion 13S of the piston head 13 and the retainer support portion 15D (fig. 7) of the retainer 15 may have a predetermined circular arc shape in cross section and may be configured to support the head-side end portion 141 and the retainer-side end portion 142. Even in this case, the head-side end 141 and the holder-side end 142 can swing (rotate relatively) in the radial direction while contacting each other along the circular arc lines of the piston head 13 and the holder 15. Therefore, the radial oscillation of the piston head 13 is absorbed at the time of the rotation of the cylinder 12.

(3) In the above-described embodiment, the retainer bushing 11A has a continuous spherical shape along the rotation direction of the rotating shaft 11, but the present invention is not limited to this. As long as the retainer bush 11A is capable of swingably supporting the retainer 15, a part of the spherical shape may be discontinuously arranged at intervals in the rotation direction.

Description of the reference numerals

1 piston pump

1A piston motor

10 casing

100 drive part

11 rotating shaft

11A retainer bushing

11B retainer lining sphere (outer lining surface)

11C ball pin (ball pin) (projection)

12 cylinder body

12S cylinder

13 piston head (piston)

13S piston head support part (1 st connecting part)

14 piston rod

141 head side end (one end)

142 holder side end (other end)

15 holder

15A retainer spherical part (retainer inner peripheral surface)

15B bearing sliding part

15C swash plate opposed portion

15D retainer support part (2 nd connecting part)

15S spherical pin groove (groove part)

16 swash plate

161 swash plate adjusting part

162 bearing fixed part (fixed surface)

163 swash plate spherical surface part (supported part)

164 holder opposing part

17 tilting adjustment mechanism

171 swash plate supporting part

172 st tilt adjustment part

173 nd 2 nd tilt adjusting part

18 thrust bearing

19 swash plate receiving part (swash plate supporting part)

19A spherical surface

25 valve plate

Center of SC sphere

SP1 No. 1 imaginary sphere

SP2 sphere 2.

Claims

1. A hydraulic rotary machine of a variable capacity type, characterized in that,

comprising:

a housing;

a rotating shaft rotatably supported by the housing;

a cylinder block including a plurality of cylinders disposed at intervals around the rotary shaft and rotating around a central axis of the rotary shaft integrally with the rotary shaft;

a plurality of pistons which are respectively accommodated in the plurality of cylinders of the cylinder block and reciprocate in the cylinder along the axial direction of the cylinder as the cylinder block rotates;

a retainer bush including a bush outer circumferential surface having a spherical surface shape that is convex outward in a radial direction of the rotating shaft, and supported by the rotating shaft so as to be rotatable around the central axis together with the rotating shaft;

a retainer including a retainer inner circumferential surface having a concave spherical shape disposed to face the bushing outer circumferential surface, and supported by the retainer bushing so as to be swingable about an axis perpendicular to the rotation axis;

a plurality of piston rods arranged to extend in the axial direction, each of the plurality of pistons being connected to the retainer, and rotating the retainer about the central axis in conjunction with rotation of the plurality of pistons about the central axis;

a swash plate disposed opposite to the retainer on a side opposite to the cylinder block in the axial direction, and supported by the housing so as to be swingable around the axis;

a thrust bearing interposed between the swash plate and the retainer in the axial direction, the thrust bearing supporting the retainer so that the retainer can rotate around the central axis with respect to the swash plate; and

a tilt adjusting mechanism for adjusting the amount of axial movement of the piston in the reciprocating motion by swinging the swash plate about the axis, while relatively displacing the inner circumferential surface of the retainer and the outer circumferential surface of the bushing, and swinging the retainer about the axis via the thrust bearing;

the retainer bushing has at least one protrusion protruding from the bushing outer circumferential surface toward the outside in the radial direction, and a distal end portion of the protrusion in the outside direction in the radial direction has a spherical shape;

at least one groove portion extending in a swinging direction of the retainer around the axis and having a concave circular shape when viewed in a cross section orthogonal to the central axis is formed in the retainer inner peripheral surface;

the retainer and the retainer bushing are integrally rotatable around the central axis by the engagement of the at least one protrusion with the at least one groove, and the retainer is swingable around the axis by the movement of the at least one protrusion in the at least one groove.

2. A hydraulic rotary machine according to claim 1,

the at least one protrusion includes a plurality of protrusions arranged at intervals along a rotation direction of the rotation shaft;

the at least one groove includes a plurality of grooves arranged at intervals along the rotation direction.

3. A hydraulic rotary machine according to claim 2,

the curvature of the circular shape of the plurality of groove portions is set to be the same as the curvature of the spherical shape of the tip end portions of the plurality of protrusions.

4. A hydraulic rotary machine according to claim 2,

the plurality of projections are formed by an even number of projections arranged at equal intervals around the central axis;

the plurality of grooves are formed by the same number of grooves as the plurality of projections, which are arranged at equal intervals around the central axis.

5. A hydraulic rotary machine according to claim 4,

the plurality of pistons are constituted by an odd number of the pistons arranged at equal intervals around the central axis;

the plurality of piston rods are constituted by the same number of piston rods as the plurality of pistons arranged at equal intervals around the central axis.